Vacuum pallet type screen printing machine with registration means

ABSTRACT

This disclosure is directed to a pallet type screen printing machine in which a pallet is indexed to a printing station when an article supported thereon is screen printed. A feed table with guides is cooperatively disposed relative to the pallet at a feed station to facilitate the accurate positioning of a work piece onto the pallet. The machine comprises an endless drive for effecting movement of one or more pallets to and from a printing station in an endless path whereby the face of the pallet is always maintained in a face up position. The pallet is formed to define a vacuum chamber which is operatively connected to a source for drawing a negative pressure thereon. A flexible coupling operatively connects the pallet to the endless drive to permit limited movement of the pallet so that the pallet may be brought into accurate registration with the printing head at the printing station. Registration of the pallet in the printing station is effected by a locating cam and a cooperatively associated cam follower, which when activated, will effect the required alignment and registration of the pallet with the printing head.

[ Oct. 9, 1973 VACUUM PALLET TYPE SCREEN PRINTING MACHINE WITI-IREGISTRATION MEANS David Jafia, Fairlawn, NJ.

[73] Assignee: Precision Screen Machines Inc.,

Hawthorne, NJ.

[22] Filed: Mar. 4, 1971 [21] Appl. No.: 120,819

[75] Inventor:

[52] US. Cl. 101/126, 101/407 BP [51] Int. Cl B4lf15/20 [58] Field ofSearch 101/114, 115,117,

101/118, 126, 123,124, 37, 407 R, 407 A, 407 BP; 198/138; 248/363 [56]References Cited UNITED STATES PATENTS 3,536,004 10/ 1970 Derrickson10l/407 R 2,846,946 8/1958 Schwarzberger.. 101/115 3,261,281 7/1966l-lartmeister... 101/40 3,429,544 2/1969 Williams 248/363 X 3,218,96711/1965 Childress... 101/114 662,709 11/1900 Clay 198/138 3,260,3517/1966 Miller 198/138 3,405,795 10/1968 Maschera 198/138 3,339,6989/1967 l-lartmeister et al. 101/40 X 3,543,679 12/1970 Wahl 101/353,486,441 12/1969 Hillman et al. 101/35 3,459,125 8/1969 Forsland 101/35Primary Examiner-Robert E. Pulfrey Assistant Examiner-R. E. SuterAttorney-lrving Seidman [5 7] ABSTRACT This disclosure is directed to apallet type screen printing machine in which a pallet is indexed to aprinting station when an article supported thereon is screen printed. Afeed table with guides is cooperatively disposed relative to the palletat a feed station to facilitate the accurate positioning of a work pieceonto the pallet. The machine comprises an endless drive for effectingmovement of one or more pallets to and from a printing station in anendless path whereby the face of the pallet is always maintained in aface up position. The pallet is formed to define a vacuum chamber whichis operatively connected to a source for drawing a negative pressurethereon. A flexible coupling operatively connects the pallet to theendless drive to permit limited movement of the pallet so that thepallet may be brought into accurate registration with the printing headat the printing station. Registration of the pallet in the printingstation is effected by a locating cam and a cooperatively associated camfollower, which when activated, will effect the required alignment andregistration of the pallet with the printing head.

17 Claims, 15 Drawing Figures PATENTED [1U 1 73 SHEEI 2 BF 6 INVENTORJAFFA DAVID W fl me ATTOR N EY PATENTEDUBT 9M3 3.763.776

SHEET 0F 6 v INVENTOR DAV/D JAFFA ATTORNEY PATENTEDUBT SIQYS sum 5 or 6INVENTOR DAV/ D JAFFA BY KM MM ATTORNEY PATENTED 9 I973 SHEET 6 OF 6INVENTOR JAFFA ATTORNEY BY DAV/D I k/fl A 1 V CUUM PALLET YPE SCREEN PRITI G MACHINE WITH REGISTRATION MEANS PROBLEM AND PRIOR ART It is nowknown in thescreen printing art that endless conveyor means in the formof an endless belt can be utilized for effecting the movement of anarticle to be printed to and from a printing section. N ori-por'ousarticles are maintained in position on such endless belts duringmovement by drawing a vacuum on the belt and the article supportedthereon. Poro'us articles, e.g'., cloth, are adhesively secured to thesurface of the belt. However, in either event, i.e. 'whe'th'er thearticle was maintained in position either by vacuum or adhesive,accurate registration of the article supported on such endless belt withthe printing head presented some difficulties because indexing of thebelt would have to be effected over relatively long distances. Theproblem was particularly aggrevated in multi-colored printing machineshaving lengths extending 50 feet or more depending on the number ofcolor printing stations. Some of the registration difficulty resultedfr'cim the stretch induced in such belts over such long distances; Alsowhen such endless belts were subjected to a vacuum; it was necessary tocontrol the mode of operation (or function) of the vacuum acting on thebelt and article supported thereon by changing from that of an articleholding vacuum to that of an article indexing vacuum when the printingof an article atone location was completed. Consequently during thechange of the vacuum function from holding to indexing, difficulty wassometimes encounteredin prohibiting the article from shifting andthereby adversely affecting the registration of the article with aprinting head. Also where long endless belts are employed it wasfrequently impossible to block out vacuum areas of the belt not utilizedfor either holding or indexing the article to be printed thereon.Consequently the holding ability of the vacuum would be diminishedaccordingly, which could effect the registration and/or holding of anarticle in position in place on the belt. Generally such conveyor belttype screen printing apparatus was particularly adapted for printingcontinuous webs, and are not particularly suitable for printingindividual unit articles such as posters, and the like. Where such beltconveyors were required to be utilized in conjunction with heaters ordryers for effecting the rapid drying of the printing inks after eachprinting operation, it was noted that the temperatures resulting fromthe drying operation could adversely affect the belts. This was becausethe belts were generally formed ofa material, e.g., a compositionrubber, or leather-like material, which rendered the dissipation orconduction of heat difficult. For these reasons the dryers had to beoperated at relative low temperatures to provide for the necessarydissipation of heat. This resulted in a slowing down of the machineoperating time, which resulted in decreased production and increasedcost.

OBJECTS An object of this invention is to provide a screen printingmachine having a movable pallet which moved toward and away from aprinting station in an endless path in a manner so that the face of thepallet is always maintained in a face up position throughout itsmovement through the endless path.

Another object is to provide a pallet screen printing machine in whichthe pallet is 'moved into accurate registration with a printing head ofa screen printing machine.

Another object is to provide a pallet screen printing machine having asource operatively connected to the pallet for drawing a negativepressure on the pallet as it is being moved to and away from a printingstation to maintain an article to be printed firmly secured thereto. 7

1 Another Object is to provide a screen printing maehine having aplurality of movable pallets in which each pallet is independentlyevacuated to draw a vacuum thereon for maintaining the article inposition on the respective pallets as the respective pallets are movedfrom station to station.

Another object is to provide a screen printing machine with movablepallets traveling in an endless path from printing station to printingstation having improved means for effecting the transfer of therespective pallets between the respective flights of the endless path.

Another object is to provide a flexible coupling which permits limitedrelative movement of the pallet in a printing station to insure accurateregistration of the article supported thereon with the printing head.

BRIEF SUMMARY OF THE INVENTION The foregoing objects and other featuresof the invention are attained by a screen printing apparatus comprisinga frame on which one or more printing heads are movably mounted formovement between a printing and non-printing position. Each suchprinting head includes a printing screen having a stencilled design andan associated squeegee cooperatively associated therewith to define aprinting station.

One or more pallets are mounted on the frame for movement to therespective printing stations. Each pa1- let comprises spaced apart platemembers defining therebetween a vacuum chamber. Connected to each palletis an independent source for drawing and maintaining a negative pressureon the vacuum chamber of the associated pallet. Rollers are connected toeach pallet for supporting the pallet in rolling engagement with asupporting track extending along the frame.

The means for effecting the drive of the pallets from station to stationincludes oppositely disposed flexible drive means extending along eachside of the frame. Each flexible drive means is suitably threaded overend sprockets or pulleys and is driven thereby. The respective palletsare flexibly coupled to the opposed endless drive means at opposedpoints in a manner which will permit limited movement of the palletrelative to the flexible drive means. Registration means arecooperatively associated with each pallet when in a printing station,which when actuated, will effect alignment of the pallet to bring itinto accurate registration with the associated printing head.

Transfer means are disposed adjacent each end of the frame to engage therollers of each pallet to effect the transfer of the pallet between therespective flights of the endless drive means so that the face of thepallet is always maintained in an upright position throughout themovement thereof.

The motor means for effecting the drive of the endless drive meanscomprises a fluid actuated motor which is operatively associated with adeceleration means which is operated to vary the speed of the motor soas to control acceleration and deceleration of the respective palletsdriven thereby as the respective pallets are moved into and out of therespective printing stations.

FEATURES A feature of the invention resides in the provision of aflexible coupling for securing the pallet to the endless drive tofacilitate individual registration of the pallet means at each printingstation.

Another feature of this invention resides in the provision of a screenprinting machine having an endless conveyor defined by a plurality ofconnected metallic pallets reinforced by a honeycomb core whichfunctions as a very good heat conductor to effect the rapid dissipationof the heat when the apparatus is utilized in conjunction with a dryeror heater.

Another feature of this invention resides in the provision of a screenprinting machine having an endless conveyor formed of a plurality ofconnected pallets, each having a vacuum chamber and a connected sourcefor inducing a negative pressure on the chamber.

Another feature of this invention resides in a screen printing machinehaving an endless conveyor formed of a plurality of pallets with meansfor effecting individual registration of each pallet in a printingstation.

Another feature of this invention resides in the provision of a screenprinting apparatus having an endless conveyor formed ofa plurality ofpallets with means for continuously maintaining a negative pressure onthe pallet as it is advanced from station to station.

Another feature of this invention resides in a screen printing machinehaving an endless conveyor formed of a plurality of pallets in which anindividual unit article to be printed is carried on the respectivepallets from station to station, each pallet being flexibly coupled toan endless driving means whereby the pallet may be moved relative to thedriving means to effect alignment of the pallet and article supportedthereon with a printing head.

Another feature of this invention resides in the provision of a screenprinting machine having one or more pallets moving to and away from aprinting station in an endless path wherein the pallet is alwaysmaintained in a face up position throughout its movement in the endlesspath.

Another feature of this invention resides in a pallet which is securedto an endless drive by means ofa pair of oppositely disposed flexiblecouplers or bearings.

Another feature of this invention resides in the provision of aregistration means cooperatively associated with each pallet whendisposed in a printing station to effect accurate registration of thepallet with its printing head.

Another feature of this invention resides in the provision of a transfermeans disposed at each end of the endless path arranged to guide one endof the pallet for effecting the transfer of the pallets from one flightto another of the endless drive in a manner wherein the pallet ismaintained in a face up position.

Another feature of this invention resides in a drive means for effectingthe drive of the pallet in a manner wherein the acceleration anddeceleration of the pallet as it is moved into and out of printingposition is controlled.

Other features and advantages will become more readily apparent whenconsidered in view of the drawings and detailed description wherein:

FIG. 1 is a side elevation view of a screen printing machine embodyingthe present invention having portions thereof broken away, and otherportions thereof diagrammatically illustrated.

FIG. 2 is a side elevation view of the track subassembly of the frame ofFIG. 1 and having portions thereof broken away.

FIG. 3 is a top planview of the track sub-assembly of FIG. 2 havingportions thereof broken away.

FIG. 4 is a top plan view of the frame construction of FIG. 1.

FIG. 5 is a sectional end view taken along line 55 on FIG. 1.

FIG. 6 is a detailed end view of a pallet construction utilized in thescreen printing machine of FIG. 1.

FIG. 7 is a detailed bottom view of the pallet construction of FIG. 6.

FIG. 8 is a side elevation view of the pallet construction of FIGS. 6and 7.

FIG. 9 is an enlarged detail of the flexible connection between thepallet and the drive means.

FIG. 10 is a detailed sectional view of the pallet means taken alongline 10-10 on FIG. 1, as supported on its track.

FIG. 11 is a detailed sectional view of the pallet means and associatedregistration means when disposed in printing position in a printingstation.

FIG. 12 is a plan view of the pallet and associated registration meansof FIG. 11.

FIG. 13 is an end view of a detail of construction of the pallet meansillustrating the electrical coupling between the pallet means and itsassociated vacuum pump.

FIG. 14 is a side elevation view illustrating the motor drive means forthe endless drive embodied in the apparatus of FIG. 1.

FIG. 15 is an end elevation view of the motor drive means of FIG. 14.

DETAILED SPECIFICATION Referring to the drawings there is illustratedtherein a screen printing machine 25 embodying the present invention.The screen printing machine 25 comprises a frame 26 defined by opposedlongitudinally extending side members 27 which are interconnected atspaced intervals by transversely extending tie members 28. Connected toeach side of the longitudinally extending side members are a pluralityof vertically disposed leg structures 29 for supporting the frame on asuitable supporting surface. As best seen in FIG. 1 the frame 26 may bemade in any predetermined length for accommodating one or more printingstations or printing heads 30.

In the illustrated embodiment a plurality of printing heads 30 aredisposed at spaced intervals along the length of frame 26, for colorprinting, each head 30 being used to print a different color. Eachprinting head 30 is suitably connected to the frame 26 for movementbetween a raised non-printing position and a lowered printing position.The respective printing heads 30 comprise a head support frame 31(schematically illustrated) which is constructed to support thereon aprinting screen 32 and an associated squeegee bar 33 and/or flood bar(the latter now shown), the squeegee forcing the printing inks throughthe ste'ncilled portion of the printing screen 32 during a printingoperation. The means for effecting the raising and lowering of theprinting head 30 between a printing and non-printing position are wellknown in the art and consequently a detailed description thereof is notconsidered pertinent to an understanding of the present invention.

Each printing head 30 disposed along the length of the machine framedefines a printing station in which the printing is done. If desired theprinting heads 30 may be spaced along the frame 26 at spaced intervalsfor accommodating therebetween a dryer or heater for effecting thedrying of the printing inks as may be required during certain printingoperations.

Mounted on the frame 26 between the longitudinally extending sidemembers 27-27 are opposed track forming members 34 to define a trackwayon which a pallet 35 is movably supported along the length of the frame26 for moving toward and away from the respective printing stations 30.As best seen in FIGS. 2, 3 and 5, the track means 34 are arranged todefine an upper track section 36 and a lower track section 37 of anendless pathway for the pallet 35, as'will be hereinafter described,along the frame structure. As best seen in FIG. 5 the upper and lowertracks 36, 37are similarly constructed, each track 36, 37 being definedby oppositely disposed angle members 36A, 36A and 37A, 37A, respectivelywhich are suitably secured to a bracket or support 39 extending inwardlyfrom the opposed side structure 27 of the machine frame. The horizontalflange of the opposed track members 36A, 36A and 37A, 37A defines therail portion for supporting the pallet rollers 40 mounted on each sideof the pallet means 35, as will be hereinafter defined.

Each pallet 35 is disposed in rolling engagement with the rail or track36, 37 to transverse thereover as will be herein defined.

Cooperatively associated adjacent each rail or track member 36A, 36A and37A, 37A is a channel-shaped member 41 which forms a guide or housing toaccommodate the flights of an endless flexible drive 42. The endlessflexible drive 42 in the illustrated embodiment comprises a chain 42, ofconnected links 428, suitably threaded about end sprockets 43 and 44rotatably journalled adjacent the opposed ends of the frame. It will beunderstood that a flexible drive 42 extends along each side of the frame26. See FIG. 5. Drive chains 42 define an endless path through which therespective pallets 35 connected thereto are moved. The pallets 35 areconnected to the opposed chain drive 42 so as to be driven thereby. Eachpallet 35 is defined by an upper and lower plate member 35A, 358 whichare suitably interconnected by a circumscribing end wall 35C to definetherebetween a vacuum chamber 38. As best seen in FIG. an open latticeor honeycomb-like structure 38A is interposed between the respectiveplate members 35A, 358 to provide the necessary reinforcement. The upperplate member 35A is also provided with a series of small apertures 45disposed in open communication with the vacuum chamber 38 de- As bestseen in FIGS. 10 and 11 the respective pallets 35 are connected to theopposed drive chains 42 by a flexible bearing or coupling means 46. Onthe opposed side portions of the respective pallets 35 adjacent theleading end of the pallet 35 there is provided a chain attachmenthousing 47. The housing 47 is slightly oval and is adapted to receive aflexible coupling or bearing 48. The flexible bearing or coupling 48comprises a member formed of a resilient material, as for example,rubber or the like, which may be provided with one or more bores oropenings 48A (See FIG. 9) extending therethrough. Connected to thebearing 48 is a pin or link 49 which connects to the rollers 42A of thedrive chains 42. In operation the flexible bearing defines the driveconnection for the pallet, and functions as a cushion to permit relativelimited movement of the pallet 35 relative to the drive chains 42, aswill be hereinafter described in more detail. The arrangement is suchthat each pallet 35 is connected by opposed attachments 46-46 to therespective drive chains 42 to define a twopoint attachment for therespective pallets and in driving chains 42.

As seen in FIGS. 6 to 8 the respective pallets 35 have connected to theopposed sides, front and rear rollers fined between the plate members35A, 35B. The bottom member 35B is rendered imperforate and thereinforcing honeycomb-like structure is made so that the cells thereofare disposed in communication or interconnected to permit the free flowof air within said chamber 38.

40A and 40B by which the pallet 35 is disposed in rolling engagementwith the rail members 36A, 36A, 37A, 37A. The arrangement is such thatas the endless chains 42-42 are driven, the respective pallets 35connected therebetween will be pulled along the length of the frame formovement from station'to station.

Operatively associated with each of the pallets 35 is an electricallyoperated vacuum pump 52 which is suitably secured to the underside ofthe pallet 35, and is carried therewith as the pallet is moved along 4helength of the frame in its endless path. The outlet of the pump 52 issuitably connected in communication with the interior or the vacuumchamber 38 of the associated pallet 35 through a connecting conduit 53.Each pallet 35 is thus provided with its own independent pump fordrawing a vacuum pressure on the chamber 38 of the pallet means 35.

The vacuum pump is activated by an electric motor means 52A. Theoperation is such that the vacuum, when utilized, is maintainedcontinuously operative as the pallet 35 is advanced from station tostation. The operation of the vacuum pump is rendered continuouslyoperative by an electric commutating track 55, see FIG. 13, extendingalong the frame. The electric track 55 (See FIGS. 3 and 13) is providedwith suitable electric rails or conductors 55A which are operativelywired in an electric circuit to a source of electrical energy. (Notshown.) Connected to the underside of each pallet is an electric trolleymeans 56 which is adapted to ride in electrical contact with theelectric rails or conductors 55A. The trolley 56 in turn is electricallyconnected to the motor 52A of the vacuum pump so that when trolley 56 iselectrically connected to electrical rails 55A, the motor 52A and vacuumpump is energized; and it is maintained energized as long as trolley 56is maintained in sliding contact with electric rail 55A.

As best seen in FIG. 4, the electric track 55 comprises two sections 55Band 55C, each supporting electrical conducting rails 55A. The mainportion 55B of the electric track 55 extends beyond the feed station FSand continues along the remaining length of the frame 26. Thearrangement is such that when the pallet trolleys 56 ride this portion55B of track 55, the vacuum pump 52 is activated if current is flowingthrough conductors track 55 55A or B. Thus once the electric trolley 56of the pallets 35 engages track section 55B, the vacuum pump 52 ismaintained constantly activated as the pallets 35 advance from stationto station. A second portion 55C of the track 55 which forms thecontinuation of the first track portion 55B, but with the conductingrails electrically insulated from those of sections 55B, is disposed atthe feed station PS. This second track portion SSC is operativelyconnected to a suitable switch (not shown) so that the current flowingthrough the conducting rails of this section of the track SSC iscontrolled independently of track section 55B. The switch controllingthe current to track section 55C can be actuated by an operator at thewill of the operator to facilitate the positioning of an article on thepallet 35 associated with track section 55C, without affecting thevacuum operating on the other pallets 35. In operation, an operatorfeeding the articles to be printed on the pallet 35 in the feed stationFS will normally deactivate the vacuum pump 52 operating on the palletin the feed station when placing the article to be printed thereon. Whenthe article has been properly orientated into its proper position on thepallet 35 in the feed station FS, the operator then will energize thevacuum pump 52 to draw the vacuum on the pallet in the feed station tomaintain the article orientated in position thereon. Thus at the feedend of the machine the vacuum pump can be operated between an on and offposition. As the pallet in the feed station FS advances to the firstprinting station, the trolley 56 connected thereto slides off portion55C and onto portion 55B of the electric track. In doing so the vacuumpump 52 of the pallet 35 is brought under the influence of the currentflowing through track portion 558 whereby it functions to maintain thevacuum pump 52 actuated throughout the movement of the pallet 35 throughthe succeeding printing stations. As the trolley 56 of the pallet 35 ismoved beyond the end of track section 55B, the current flow to thevacuum pump motor is interrupted, thereby releasing the vacuum onchamber 38. When this occurs the article which has been printed can beremoved from the pallet 35.

Each pallet 35 is provided with independent means for effectingregistration of the pallet 35 with respect to an associated printinghead 30 when the pallet 35 has been advanced to a printing station. Thearrangement is such that the pallet 35 can be accurately registered toaccommodate or compensate for any slack or play in the flexible drive42. As the respective pallets 35 are connected to the respective endlessdrives 42 by a two-point connection, each containing a flexible bearingor coupling 48, the pallets 35 may be moved or shifted relative to thechain 42 an amount sufficient to bring the respective pallets 35 inaccurate registration with the printing head 30. The means for effectingthe registration of the pallet 35 at the printing station comprises a anangled member 60 connected to the undersurface of the pallet 35. As bestseen in FIGS. 6 and 7, the horizontal flange 60A of the angled member 60is suitably secured to the bottom plate 358 of the pallet 35. Thedependent flange 608 extends downwardly from the pallet and transverselythereof. Mounted to the frame at each printing station is a bracket 61(see F i6. 11) on which a pair of spaced apart stop rollers 62 arepositioned. The stop rollers 62 function as a lateral stop to limitlateral displacement of the pallet 35 as the pallet is moved intoregistration. The arrangement is such that when the pallet 35 islaterally displaced to effect registration, lateral movement is limitedby engagement of flange 60B with stop rollers 62. When the pallet islaterally displaced for registration, the pallet 35 is squared relativeto the printing station as the flange 60B engages stop rollers 62.

The means for effecting the squaring or registration of the palletrelative to its printing head comprises a locator 63 having a V notch63A formed therein. The 10- cator 63 is connected to the dependingflange 60B of member 60. Cooperatively associated with the locator 63 isa follower in the form of a roller 64 connected to the end of a push rod65 of a piston and cylinder activating means 66. The piston and cylinderassembly 66 is suitably supported on a supporting bracket 67 connectedto the machine frame 26 in each printing station. The arrangement issuch that the push rod 65 of the roller 64 is operatively connected tothe piston rod 66A of the piston and cylinder assembly 66. Accordingly,whenever the piston and cylinder assembly 66 is actuated the push rod 65advances the roller 64 towards the notch 63A of the locator 63, and asthe roller 64 is seated into the V-notch 63A, the pallet 35 is displacedor squared accordingly as the depending flange 60B of the member 60 ismoved into abutment against the stops 62. The pallet 35 is thus squareedin registration with the printing head 30 so that the article to beprinted, supported thereon, can be located in accurate registration withthe stencilled portion of the printing screen 32 supported on theprinting head 31. As the electric trolley 56 is operatively connected incircuit to the vacuum pump 52 carried on the pallet 35 by engagement inelectrical contact with the supply of the electric track 55B, the vacuumis maintained on the pallet as it is brought into registration. Wherethe apparatus 25 is provided with a plurality of printing stations, thearrangement is such that the pallets 35 are individually capable ofbeing brought into registration at each printing station while thevacuum is maintained thereon.

As best seen in FIGS. 14 and 15 the drive means for the endless drive orchain 42 comprises a motor means. In the illustrated form of theinvention a fluid actuated or hydraulic motor 70 is employed. Thehydraulic motor 70 is operatively connected to a control valve 71 forcontrolling the fluid flow to motor 70 by which the speed of the motor70 is regulated. The output shaft 72 of the fluid motor 70 has connectedthereto a sprocket 73 which is connected in driving relationship to adrive sprocket 74 by means of a chain drive 75 interconnectedtherebetween. The drive sprocket 74 is connected to the main drive shaft76. Journalled to the main drive shaft 76 is the driving sprocket 43 ofthe endless chain drive 42. As best seen in FIG. 1 the drive sprocket 43of the drive chain 42 is connected adjacent the feed end FS of themachine. The other end of the chain drive 42 is threaded over end idlesprocket 44.

Connected to the main drive shaft 76 is a drive sprocket 77 foreffecting the indexing or advancing of the pallets 35 toward and awaythe repsective printing stations. As shown in FIGS. 14 and 15 the driveindexing sprocket 77 is connected in driving relationship to an indexingsprocket 78 by means of a connected driving chain 79. Operativelyconnected to the shaft 80 of the indexing sprocket 78 is a rotating ram81 and ram roller 81A which function to control the fluid flow to themotor 70. An actuating lever 82 is pivoted about pivot 83 for movementtoward and away from the valve 71 controlling the flow of fluid to motor70. The arrangement is such that rotation of the ram 81 and roller 81Aas the indexing shaft 80 is rotated effects displacement of the lever 82to control the actuation of valve 71. To limit the rotation of the ram81 there is provided a ram stop 84 which is actuated between operativeand inoperative position by means of a piston and cylinder assembly 85.As viewed in FIG. 14 when the ram stop 84 is raised to its upperposition, as indicated in the dotted line showing thereof, the shaft 80containing the ram 81 and ram roller 81A is permitted to rotate therebycausing the ram roller 81A to engage the actuating lever 82. Theengagement between the ram roller 81A and the actuating lever 82 is suchthat as the displacement of the actuating lever 82 activates the controlvalve 71 controlling the flow of fluid to the motor to effect the speedthereof, the arrangement is such that as the pallet 35 approaches theprinting position, the speed of the motor is gradually reduced due tothe reduction in flow of fluid thereto and thereby resulting in thecontrolled deceleration of the pallet as it reaches printing position.By effecting controlled deceleration of the pallets 35 as they reachprinting position, excessive banging and machine vibration is minimized.

To effect the transfer of the respective pallets 35 between the upperand lower flights of the chain drive as the pallets move in the endlesspath of travel, transfer means 87 and 88 are provided at each end of themachine. See FIGS. 1 and 2. The transfer means 87 and 88 cooperate withthe drive means 42 to maintain the respective pallets 35 horizontal andface up as they round the end sprockets 43 and 44. At the feed end ofthe machine the transfer means 87 includes a lifting sprocket 89rotatably journalled about a suitable shaft 90 to which a drivingsprocket 91 is journalled. As shown in FIG. 1 the periphery of thelifting or transfer sprocket 89 is provided with a series ofcircumferentially spaced notches 89A which are adapted to engage therear or lead rollers 40A of the pallets advancing or moving toward thesprocket 89 along the lower flight. The rotation of the lifting sprocket89 is timed so that the notches will engage with rollers 40A of theapproaching pallet 35 as the chain attachment or housing 47 roundssprocket 43. Timing of the lifting sprocket 89 is attained by driving itfrom the main drive shaft 76 by an auxiliary chain drive 92.

As best seen in FIG. 1, the auxiliary drive 92 comprises a drivesprocket 93 journalled to the main shaft 76. A complementary sprocket 91journalled to shaft 90 to which the lifting sprocket 89 connected, andsprockets 93 and 91 are connected in driving relationship by a drivechain 92. The rotation of the lifting sprocket 89 is thus timed to thespeed of the main chain drive 42 through appropriate gearing ratios ofthe respective sprockets.

The arrangement is such that as pallet 35 advances beyond its endsprocket 43, the lead roller 40A engages one of the notches 89A on thelifting sprocket 89 causing the associated end of the pallet to raise asthe chain attachment housing 47 rides up on the chain sprocket 43. Inthis manner both ends of the leading pallet in the lower flight areraised simultaneously as the pallets 35 are advanced from station tostation; the top of the pallet being always maintained in a face upposition.

At the discharge or other end of the machine 25, the transfer means 88is defined as a curved guide or channelway for accommodating the endrollers 40B of the respective pallets 35, as they approach the end ofthe upper flight of drive means 42. As shown in FIG. 2, the transfermeans 88 includes a curved rail section 88A which defines an extensionof rail 36A. A companion guide rail 88B is spaced from rail section 88Ato guide and confine the rollers 40B of pallet 35 as the pallet istransferred from the upper to lower flight of the chain drive 42. As theother end of the pallet is supported by the chain attachment 47, theco-action between the transfer means 88 and end sprocket 44 effect thetransfer of the endmost pallet between the upper and lower flights. Thecurve of rail section 88A and its complementary rail 88B prohibits anyvertical drop of the pallet, and as the chain attachment end 46 isguided around end sprocket 44, the following end or rollers 40B aresimilarly guided by the transfer means 88 resulting in that the palletis maintained substantially horizontal and face up as it rounds the endof the chain drive 42.

To assist in positioning an article to be printed on the pallet 35 atthe feed end of the machine, a feed table 95 is provided. As best seenin FIG. 4, the feed table 95 has an end portion which overlies a portionof the pa]- let. Guides 95A are provided on the table 95 to facilitatethe positioning of the article on the pallet so as to be in properregistration with the screen when the pallet 35 is advanced to aprinting station. By locating the guides on the table rather than thepallet the entire surface of the pallet is available for printing. Whenan operator or an automatic feeder has located the article with respectto the guides 95A on table 95, a portion of the article is supported onthe pallet. By actuating the vacuum of the pallet at the feed station,the article is secured thereto, and as the pallet is advanced throughthe feed station, it will slide the remainder of the article off thefeed table and onto the underlying portion of the pallet 35.

OPERATION OF THE MACHINE The article to be printed is loaded onto therespective pallets 35 as the pallet 35 is moved into the feeding stationFS at the feed end of the machine. The article registration onto itsrespective pallet 35 in the feed station FS is facilitated by means of afeeding table 95 which has a marginal portion overlapping or overlying apor tion of the pallet 35 in the feed station. The orientation means orguides 95A provided on the feed table assist in orientating or locatingthe article to be printed properly upon its respective pallet. When thematerial or article to be printed is properly orientated on the pallet35 in the feed station, a switch (not shown) for activating the vacuumpump 52 is energized to draw a vacuum on chamber 43 of pallet 35. Thepallet is then advanced to the first printing station whereby the vacuumbeing drawn on the chamber causes the article to be printed to beadherred thereto and to advance therewith to the printing station. Asthe pallet 35 approaches the first printing station, the pallet isdecelerated by actuation of the deceleration means described and broughtto a standstill at the printing station. To effect accurate registrationof the pallet 35 and the article supported thereon and to compensate forany slack in the drive chains 42, the piston and cylinder assembly 66 ofthe registration means is activated. When actuated the push rod 35advances the connected cam follower 64 to engage the V-notch of the camlocator which will effect displacement of the pallet an amount limitedby the engagement of the guide 60 with the guide followers or stops 62to effect the alignment of the pallet with the printing head. Theflexible coupling or bearing 48 between the pallet and drive chainspermits the pallet to be displaced. As the trolley 56 of the pallet isengaged in electrical contact with the conducting rail 55A of theelectrified track 55, the vacuum pump is maintained activated tomaintain a continuous vacuum on the pallet 35 during a printingoperation.

With the pallet 35 registered in position at the printing station, theprinting head 30 is lowered whereby the screen 32 is properly positionedin registration on the work piece or article to be printed. Theactuation of the squeegee 33 in a conventional manner will effect theprinting stroke forcing the inks or dyestuff through the design of thestencilled screen and onto the article to be printed. Upon completion ofthe printing stroke the printing head 30 is raised to an inoperative ornonprinting position. As the printing head is being raised to anonprinting position, the piston and cylinder assembly 66 of theregistration means is deactivated causing the cam follower 64 to bewithdrawn freeing the pallet for advancement to the next station. Thenthe piston and cylinder assembly 85 is actuated to index the pallet tothe next station. In a multiple color printing machine the next stationmay comprise a second printing station wherein a second color may beprinted onto the article. In event that a means is required foreffecting the drying of the ink on the article before a second color maybe applied, it will be understood that a heater or drying oven may beinterposed between successive printing stations. In this manner theprinted article may be dried as it advances to the next printingstation. However, it will be understood that the utilization of a heateror dryer with the apparatus as described is optional depending upon thenature and type of screen printing operation being performed.

To advance or index the respective pallets 35 to the next station,piston and cylinder assembly 85 is energized to release the ram stop andeffect the movement of the indexing means and associated drive means 42.

in doing so, the actuation of the ram 81 on the deceleration lever 82controlls the flow of fluid to the fluid drive motor accordingly toeffect the acceleration and /or the deceleration of the pallet drivingmeans.

The construction of the pallets described is such that it constitutes agood heat conductor and when used in conjunction with a dryer or heater,will function to effect the rapid dissipation of the heat therefrom. Forthis reason dryers may be operated at higher heat temperatures topromote faster drying, and thereby increase the machine output, orconversely reduce the cycling time of the apparatus. Also the palletsare not adversely affected by the heat output of such heating means whenutilized in conjunction therewith.

It will be noted that the apparatus described is particularly applicablefor use in printing non-porous material. However, it will be understoodthat porous type material can also be screen printed by the apparatusdescribed. This can be attained either by coating the top of the pallets35 with a suitable adhesive by which the porous material may then besecured thereto without the intervention of the vacuum means, oroptionally the porous material to be printed may be suitably secured toa non-porous backing sheet by suitable adhesive, which backing sheet inturn is maintained in position on the respective pallets through theinteraction of the vacuum means. While the instant invention has beendescribed with respect to a particular embodiment thereof it willreadily appreciated and understood that variations and modifications maybe made without departing from the spirit or scope of the invention.

What is claimed is:

l. A screen printing machine comprising a frame,

a printing head defining a printing station mounted on said frame,

a track means on said frame extending along the length of said frame,

a pallet means movably mounted on said track,

said pallet means including spaced apart upper and lower plates andconnected end walls defining therebetween a vacuum chamber,

said upper plate having a series of apertures formed therein,

means connected to said pallet means for drawing a vacuum on saidchamber,

spaced apart roller means connected to said pallet means disposed inrolling contact with said track means,

a flexible endless drive disposed along each side of said frame,

said endless drive including an upper flight and a lower flight,

a flexible coupling connecting said pallet means to each of said endlessdrivers,

motor drive means connected to said endless drive to effect theactuation thereof for moving the connected pallet toward and away fromsaid printing station, means for effecting registration of said palletmeans with said printing head when in the printing station,

and transfer means adjacent each end of said endless drives foreffecting movement of said pallet means between said upper and lowerflights, said transfer means always maintaining said pallet means faceup.

2. The invention as defined in claim 1 and including an electric track,

and a sliding contact engaging said electric track,

said contact being connected in circuit to said vacuum drawing means,whereby said latter means is energized when said sliding contact isdisposed in electrical contact with said track.

3. The invention as defined in claim 1 wherein said registration meansincludes a locator having a notch carried on said pallet means,

and a cooperating follower positioned on the frame to engage saidlocator notch,

and means for activating said follower.

4. The invention as defined in claim 1 wherein said transfer meansincludes a transfer sprocket adjacent one end of said machine,

and a transfer guide means at the other end of the machine,

means formed on the periphery of said transfer sprocket for receivingsaid rollers whereby said sprocket when engaged by said rollersfunctions to transfer said pallet means, face up, between said flights.

5. The invention as defined in claim 1 and including indexing meansconnected to said motor drive means to limit the movement of said palletmeans to said printing station.

6. The invention as defined in claim 1 and including means fordecelerating the speed of said motor drive means as said pallet meansapproaches said printing station.

7. The invention as defined in claim 1 wherein said pallet meansincludes roller means, and said transfer means at one end of said flightcomprising:

a transfer sprocket,

means for driving said transfer sprocket in unison with said drivemeans,

said transfer sprocket having means formed about the periphery thereoffor engaging the roller means connected to said pallets, whereby saidtransfer sprocket co-acts with said drive means to lift said palletsfrom the lower flight to the upper flight.

8. In a screen printing machine including a frame having a feed end, anda screen printing head mounted on said frame for movement betweenprinting and nonprinting position, the improvement comprising:

pallet means, said pallet means having an upper and lower memberdefining a chamber therebetween, said upper member having aperturesformed therein,

a drive means for effecting the movement of said pallet means toward andaway from a printing station located below said printing head,

said drive means comprising an endless flexible drive moving in anendless path along spaced apart upper and lower flights,

means connecting said pallet means to said endless flexible drive to bedriven along said endless path,

transfer means disposed adjacent the opposed ends of said endless pathfor effecting the transfer of said pallets between said flights, saidtransfer means maintaining said pallets in a face-up position throughoutthe travel thereof along said endless path,

a vacuum producing means connected to the chamber of said pallet meansfor drawing a negative pressure on said chamber as said pallet meansmoves along said endless path,

a registration means operatively associated with said pallet means foreffecting registration of said pallet means withsaid printing head whenin the printing position beneath said printing head.

9. The invention as defined in claim 8 wherein said pallet connectingmeans includes a resilient coupling to provide for limited relativemovement between said pallet means and its flexible drive.

10. The invention as defined in claim 9 wherein said drive meansincludes:

a pair of spaced apart endless flexible driving means extending alongthe longitudinal sides of said frame,

said resilient coupling means comprising opposed connecting linksdisposed to opposed sides of said pallet,

one end of said link being connected to the adjacent flexible drivemeans,

a resilient bearing member connected to the other end of said link,

and a bearing housing connected to the sides of said pallet means forreceiving said resilient bearing member.

11. The invention as defined in claim 9 wherein said drive meansincluding a pair of opposed endless flexible drives, said pallet beingdisposed between said flexible drives,

said resilient coupling means are oppositely disposed on said palletmeans to form a connection with the respective endless drives wherebysaid flexible drives pull said pallet therebetween to and from aprinting station when actuated,

and said registration means comprising a locating means connected tosaid pallet and,

a complementary follower positioned on the frame to engage said locatingmeans,

and means for activating said follower to effect registration of saidpallet means in the printing station.

12. The invention as defined in claim 8 and including a feed tabledisposed to one side of the pallet means at the feed end of saidmachine,

said feed table extending slightly over the side of said pallet means inoverlying relationship thereto,

and means on said table for properly orientating a work piece on saidpallet means whereby the workpiece is partly supported on said feedtable and partly on said pallet means at the feed end.

13. The invention as defined in claim 8 wherein said pallet meansincludes roller means, and said transfer means at one end of said flightcomprises a transfer guide means positioned to receive the roller meansof said pallet, and to cooperate with said drive means for effectingtransfer of said pallet means between the upper and lower flight in saidface-up position.

14. The invention as defined in claim 8 and including means formaintaining said vacuum producing means actuated as said pallet means ismoved toward and away from said printing station.

15. In a screen printing machine having a frame and a plurality ofprinting heads mounted on said frame to define a plurality of printingstations, each of said printing heads being adapted to support aprinting screen and an associated squeegee,

the improvement comprising,

a plurality of pallet means supported on said frame by drive meanshaving endless vertically spaced aparts flights,

said endless drive means for effecting the movement of said pallet meansfrom station to station along said flights in an endless path,

means for flexibly coupling each of said pallet means to said endlessdrive means at spaced intervals along said endless drive means,

means for effecting the registration of said pallet means with itsrespective printing head when disposed in said printing stations,

each of said pallet means including spaced apart upper and lower membersdefining a chamber therebetween, said upper member having aperturesformed therein,

a vacuum producing means connected to each of said pallet means fordrawing a negative pressure on the associated pallet chamber,

means for maintaining said vacuum producing means activated as saidpallet means advances through the respective printing stations,

l l6 and transfer means adjacent each end of said endless said palletmeans,

path for maintaining said pallet means in a face-up and saidregistration means including a locator on position through the entiretravel thereof about each of said pallet means and an associated folsaidendless path. lower located on said frame at each printing sta- 16. Theinvention as defined in 5 tion, 15 wherein said endless drive meanscomprises: a means for activating said follower to effectregistraopposed flexible endless drives extending along the tion of saidfollower with said locator on said pallet adjacent longitudinal sides ofsaid frame, and means in a printing station. said flexible couplingmeans including oppositely dis- 17. The invention as defined in claim 16wherein the posed links, direction of movement of said follower issubstantially a resilient bearing connected to one end of each of normalto said locator on said pallet means.

said links, said resilient bearing being coupled to

1. A screen printing machine comprising a frame, a printing headdefining a printing station mounted on said frame, a track means on saidframe extending along the length of said frame, a pallet means movablymounted on said track, said pallet means including spaced apart upperand lower plates and connected end walls defining therebetween a vacuumchamber, said upper plate having a series of apertures formed therein,means connected to said pallet means for drawing a vacuum on saidchamber, spaced apart roller means connected to said pallet meansdisposed in rolling contact with said track means, a flexible endlessdrive disposed along each side of said frame, said endless driveincluding an upper flight and a lower flight, a flexible couplingconnecting said pallet means to each of said endless drives, motor drivemeans connected to said endless drive to effect the actuation thereoffor moving the connected pallet toward and away from said printingstation, means for effecting registration of said pallet means with saidprinting head when in the printing station, and transfer means adjacenteach end of said endless drives for effecting movement of said palletmeans between said upper and lower flights, said transfer means alwaysmaintaining said pallet means face up.
 2. The invention as defined inclaim 1 and including an electric track, and a sliding contact engagingsaid electric track, said contact being connected in circuit to saidvacuum drawing means, whereby said latter means is energized when saidsliding contact is disposed in electrical contact with said track. 3.The invention as defined in claim 1 wherein said registration meansincludes a locator having a notch carried on said pallet means, and acooperating follower positioned on the frame to engage said locatornotch, and means for activating said follower.
 4. The invention asdefined in claim 1 wherein said transfer means includes a transfersprocket adjacent one end of said machine, and a transfer guide means atthe other end of the machine, means formed on the periphery of saidtransfer sprocket for receiving said rollers whereby said sprocket whenengaged by said rollers functions to transfer said pallet means, faceup, between said flights.
 5. The invention as defined in claim 1 andincluding indexing means connected to said motor drive means to limitthe movement of said pallet means to said printing station.
 6. Theinvention as defined in claim 1 and including means for decelerating thespeed of said motor drive means as said pallet means approaches saidprinting station.
 7. The invention as defined in claim 1 wherein saidpallet means includes roller means, and said transfer means at one endof said flight comprising: a transfer sprocket, means for driving saidtransfer sprocket in unison with said drive means, said transfersprocket having means formed about the periphery thereof for engagingthe roller means connected to said pallets, whereby said transfersprocket co-acts with said drive means to lift said pallets from thelower flight to the upper flight.
 8. In a screen printing machineincluding a frame having a feed end, and a screen printing head mountedon said frame for movement between printing and non-printing position,the improvement comprising: pallet means, said pallet means having anupper and lower member defining a chamber therebetween, said uppermember having aPertures formed therein, a drive means for effecting themovement of said pallet means toward and away from a printing stationlocated below said printing head, said drive means comprising an endlessflexible drive moving in an endless path along spaced apart upper andlower flights, means connecting said pallet means to said endlessflexible drive to be driven along said endless path, transfer meansdisposed adjacent the opposed ends of said endless path for effectingthe transfer of said pallets between said flights, said transfer meansmaintaining said pallets in a face-up position throughout the travelthereof along said endless path, a vacuum producing means connected tothe chamber of said pallet means for drawing a negative pressure on saidchamber as said pallet means moves along said endless path, aregistration means operatively associated with said pallet means foreffecting registration of said pallet means with said printing head whenin the printing position beneath said printing head.
 9. The invention asdefined in claim 8 wherein said pallet connecting means includes aresilient coupling to provide for limited relative movement between saidpallet means and its flexible drive.
 10. The invention as defined inclaim 9 wherein said drive means includes: a pair of spaced apartendless flexible driving means extending along the longitudinal sides ofsaid frame, said resilient coupling means comprising opposed connectinglinks disposed to opposed sides of said pallet, one end of said linkbeing connected to the adjacent flexible drive means, a resilientbearing member connected to the other end of said link, and a bearinghousing connected to the sides of said pallet means for receiving saidresilient bearing member.
 11. The invention as defined in claim 9wherein said drive means including a pair of opposed endless flexibledrives, said pallet being disposed between said flexible drives, saidresilient coupling means are oppositely disposed on said pallet means toform a connection with the respective endless drives whereby saidflexible drives pull said pallet therebetween to and from a printingstation when actuated, and said registration means comprising a locatingmeans connected to said pallet and, a complementary follower positionedon the frame to engage said locating means, and means for activatingsaid follower to effect registration of said pallet means in theprinting station.
 12. The invention as defined in claim 8 and includinga feed table disposed to one side of the pallet means at the feed end ofsaid machine, said feed table extending slightly over the side of saidpallet means in overlying relationship thereto, and means on said tablefor properly orientating a work piece on said pallet means whereby theworkpiece is partly supported on said feed table and partly on saidpallet means at the feed end.
 13. The invention as defined in claim 8wherein said pallet means includes roller means, and said transfer meansat one end of said flight comprises a transfer guide means positioned toreceive the roller means of said pallet, and to cooperate with saiddrive means for effecting transfer of said pallet means between theupper and lower flight in said face-up position.
 14. The invention asdefined in claim 8 and including means for maintaining said vacuumproducing means actuated as said pallet means is moved toward and awayfrom said printing station.
 15. In a screen printing machine having aframe and a plurality of printing heads mounted on said frame to definea plurality of printing stations, each of said printing heads beingadapted to support a printing screen and an associated squeegee, theimprovement comprising, a plurality of pallet means supported on saidframe by drive means having endless vertically spaced aparts flights,said endless drive means for effecting the movement of said pallet meansfrom station to stAtion along said flights in an endless path, means forflexibly coupling each of said pallet means to said endless drive meansat spaced intervals along said endless drive means, means for effectingthe registration of said pallet means with its respective printing headwhen disposed in said printing stations, each of said pallet meansincluding spaced apart upper and lower members defining a chambertherebetween, said upper member having apertures formed therein, avacuum producing means connected to each of said pallet means fordrawing a negative pressure on the associated pallet chamber, means formaintaining said vacuum producing means activated as said pallet meansadvances through the respective printing stations, and transfer meansadjacent each end of said endless path for maintaining said pallet meansin a face-up position through the entire travel thereof about saidendless path.
 16. The invention as defined in claim 15 wherein saidendless drive means comprises: opposed flexible endless drives extendingalong the adjacent longitudinal sides of said frame, and said flexiblecoupling means including oppositely disposed links, a resilient bearingconnected to one end of each of said links, said resilient bearing beingcoupled to said pallet means, and said registration means including alocator on each of said pallet means and an associated follower locatedon said frame at each printing station, a means for activating saidfollower to effect registration of said follower with said locator onsaid pallet means in a printing station.
 17. The invention as defined inclaim 16 wherein the direction of movement of said follower issubstantially normal to said locator on said pallet means.